CrossRoads:
Is definitely supported. Browse the forum, has been posted about often.
Supported only in the sense that you can bypass the Arduino environment to directly access the AVR hardware in C/C++.
The reference manual will mislead most people using Arduino's (beginners)
Most Arduino boards have two external interrupts: numbers 0 (on digital pin 2) and 1 (on digital pin 3). The table below shows the available interrupt pins on various boards.
Board int.0 int.1 int.2 int.3 int.4 int.5
Uno, Ethernet 2 3
Mega2560 2 3 21 20 19 18
Leonardo 3 2 0 1 7
Due (see below)The Arduino Due board has powerful interrupt capabilities that allows you to attach an interrupt function on all available pins.
Anyway, I did do the search for the OP and found a Playground page with an example of how to use the PCINT mechanism, though I would suggest that they restrict themselves to the Arduino AttachInterrupt mechanism and those pins it supports until they get more comfortable with the environment.